🕊 FREE-FORM LAB · PAGE 4

Structural anchors. Every follower on pages 1-3 measures its reach in BARS around the clock, which is right for ordinary playing and blind to the two jumps a performer makes on purpose: a fermata, whose length is theirs and not the engraver's, and a repeat, which they may simply not take. Measured on the Waldstein performance of 2026-09-01 — the fermata at bar 13 put the clock 3.4 s behind, and the exposition repeat put it a whole copy (139 s) away, where it stayed: 80-92 % of every press for the rest of the run was called a wrong note. The fermata half already ships (it is inert on four recorded runs that were tracking); the repeat and the whole-score relocalisation are the open question, because they trade wrong notes for misses. Load a run from the Recorded run tab (stats page → 🕊), or run the same comparison headless with node tools/follow_probe.mjs <song.json> <replay.json>.
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Piece

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Player

Algorithm the game uses

Takes effect on the next run you start in the game (Free Play → free-form toggle). The in-game 🕊 tempo pill names a non-default pick and shows 🔦 while the distressed layer is in charge.

How to read this

  1. Pick a player on the left. A player is a recording of someone playing — either one of your real runs (Recorded run tab; send one here with the 🕊 button next to a replay on the game's stats page) or a made-up one (Synthetic: "Steady" plays cleanly, "Fumble & carry on" does what you did at bar 20 of Feux Follets, "Breakdown + restart" flubs and restarts a bar back, etc.).
  2. ▶ Run all 10. The same playing is fed to ten different clock-following algorithms, using the real game engine.
  3. Read the sentence in the "What it did" column — ✅ it kept up with the player, ⚠️ small trouble, ❌ it ran ahead, fell behind or stopped the run. The numbers to the right say the same thing in seconds; hover a column name for its meaning. The first row is the best for this player.
  4. Click a row to see its timeline: grey = where the player was in the piece, blue = where the game's clock was. Perfect following = the lines sit on top of each other. Blue above grey = the game ran ahead (your Feux symptom). The ten little charts below compare all of them at once.
  5. When an algorithm convinces you, press its "use" button — the game plays with it from your next free-form run (the 🕊 tempo pill in the game shows its name). To compare algorithms fairly, try several players: a clean one, a messy one, and your own recordings.

Rows tie at ✅ when a player is too easy to tell the algorithms apart — that's information too (they all cope); the interesting players are the messy ones and your real runs.

Scoreboard

Run the algorithms to fill this in.
Hover a column name for what it measures. Everything is in seconds of music or in counts; Drift is the one number that summarises following quality (0 = perfect).

Timeline

player's position   follower clock   tempo estimate (right axis, × nominal)   wrong key   reclaimed note   distressed   stopped (fail overlay)

All ten at a glance